The present invention relates to clamping chuck for clamping tools by shrinkage.
A clamping chuck of this type is disclosed for example in U.S. Pat. No. 5,311,654 and in the European patent document no. EP 382 079. The clamping chuck disclosed in the prior art provide a clamping of tools by shrinkage, and an additionally for a radial clamping in the region of the tool shaft for providing a tool transmission, needs an axial support, for example an axial plane abutment on the clamping chuck. This is the case for example for special types of mills, drills or similar tools, for example having a specially designed milling cutting heads. They are provided at the rear side of the tool head with a shoulder which is suitable for an axial abutment. In known clamping chucks of this type such a rear side planar abutment is however available only during the joining process performed in heated condition. During cooling the chuck body shrinks however not only radially but also axially, so that a rear side shoulder of the tool has no planar abutment and an axial support. Therefore after a predetermined use, disadvantages are developed, for example inadequate rigidity of the chuck body with clamped-in tool, low concentric accuracy of the tool, susceptibility to vibrations, and relatively low service life of the tool.
Accordingly, it is an object of the present invention to provide a clamping chuck of the above mentioned general type, which avoids the disadvantages of the prior art.
More particularly, it is an object of the present invention to provide a clamping chuck of the above mentioned general type which guarantees a reliable planar abutment of the tool on the chuck body.
In keeping with these objects and with others which will become apparent hereinafter, one feature of present invention resides, briefly stated, in a clamping chuck in which the chuck body on its open end of the receptacle has an end-side abutment surface for the inserted tool, during insertion with a rear-side shoulder it can abut against the abutment surface, and in the region of an end portion which carries the abutment surface a ring element is arranged which in an axial direction is axially supportable on the chuck body, and forwardly on the end which axially adjoins the abutment surface, an abutment surface which is associated with the shoulder of the tool is provided for axial clamping of the inserted tool by means of the ring element relative to the chuck body.
Thereby it is possible, by means of the ring element to provide an axial clamping of the inserted tool so that the tool with its rear-side shoulder abuts against the associated abutment surface of the ring element which is axially clamped between the chuck body and the tool.
In this manner a reliable plane abutment for the tool against the chuck body is provided, whereby the strength of the chuck body together with the inserted tool is increased, the concentricity of the tool is improved, the sensitivity to vibration of the system is reduced, and finally the service life of the tool is substantially improved.
As for the ring element, the invention proceeds from the presumption that it can be advantageously a shrink ring. However, instead, it can be loaded in another manner, for example mechanically, so that the ring element is first inoperative during insertion of the tool and abutment of the same with the rear-side shoulder against the abutment surface of the chuck body, and is then actuated, when by cooling and shrinkage the longitudinal portion of the chuck body radially clamps the tool shaft in the receptacle. Due to the axial shrinkage of the longitudinal portion an axial gap between the rear-side shoulder of the tool and the end-side abutment surface of the clamping chuck is provided. Then the ring element is activated. For example by corresponding loading with mechanical forces it is moved to the inward-side shoulder of the tool until the ring element abuts with its abutment surface against the rear-side shoulder of the tool, and the tool is axially clamped in this way.
It is especially advantageous when this movement of the ring element with its design as the shrink ring is performed by corresponding truncated cone surfaces of the chuck body on the one hand and the ring element on the other hand, which narrows to the end of the chuck body or in other words to its abutment surface or to the abutment surface of the ring element. The clamping chuck in accordance with the present invention is simple, light and cost favorable. It is composed of two components, namely a one-piece chuck body on the one hand and the ring element on the other hand.
The novel features which are considered as characteristic for the present invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.